For many years, electric arc furnaces have been operated by manually controlled relay panels. As a result of competitive pressures and a desire to improve the control of arc furnaces, programmable logic controllers (PLC's) have slowly been replacing the relay panel controllers. A PLC enables continuous on-line monitoring of various furnace conditions and also serves as an input processor for higher level main frame computers which perform the heavy-duty data processing for on-line control. PLC's are generally configured to withstand the rigors of the furnace area environment, but are limited in their data processing and memory capabilities. To date, the PLC and the higher level main frame computers have performed discrete hierarchial tasks. The data processing main frame computer capabilities and the front end data collection capabilities of the PLC are integrated in a system adapted to be located on the factory level in the industrial environment of a steel mill for operation in accordance with the present invention to monitor and/or control the operation of the furnace.
The present invention employs an arc furnace monitoring system including one or more conventional PLC's and one or more conventional data processing microcomputers. The PLC's function is to perform high speed data collection of electrical, mechanical, and physical parameters of the furnace, such as, but not limited to, pulse rates from watt/var, current and potential transducers, transformer tap positions, arc length settings, hydraulic variables, positions of mechanical furnace components, and scrap charge weights and present the collected data to the data processing microcomputer in a usable format.
The present invention utilizes conventional microcomputers to receive through a high speed interface the data transmitted by the PLC in a cost effective manner and provide the operator with control information corresponding to the above identified variables by way of reports, displays and/or commands. The key to this invention consists of the integration of the PLC(s) and microcomputer(s) and the method of information handling to provide on-line data collection and data communication between the programmable logic controller and the data processing microcomputer in a stand alone unit for control of the furnace.
Accordingly, it is an object of this invention to provide an improved process to monitor and control an electric arc furnace in the manufacture of steel. It is another object of this invention to provide a stand alone on-line arc furnace monitor and control system which employs commercially available PCL's and microcomputers and eliminates the need for higher level computers.
It is still a further object of this invention to provide the operator of the furnace with process and control information and/or process commands to enable him to control the chemistry and slag characteristics of the furnace operation and more accurately predict when to charge additional scrap steel into the furnace. This, in turn, results in a more efficient utilization of the electric arc furnace.